Efficient Separation of Xe/Kr by Induced Polarization on Single-Atom Modified Ti₃C₂O₂: A DFT Study

The efficient separation of radioactive xenon (Xe) and krypton (Kr) is challenging due to their similar sizes and chemical inertness. To address this, dispersing metal atoms as single sites on a substrate can utilize their highly localized electronic structure and concentrated charge to enhance polarization of noble gas atoms, thereby achieving effective Xe/Kr adsorption and separation. Two-dimensional MXene materials, with their large specific surface areas and tunable surface terminal groups, offer promising substrates for supporting metal atoms. In this study, we performed ab initio density functional theory (DFT) calculations to systematically evaluate the adsorption and separation capabilities of transition metal (TM) functionalized Ti₃C₂O₂ (TM-Ti₃C₂O₂) for Xe and Kr. Among the tested metals, Cu-Ti₃C₂O₂ exhibited the strongest adsorption toward both gases. Charge density difference and partial density of states analyses revealed that the supported Cu atom induce significant polarization of Xe and Kr, facilitating pronounced interactions between the p orbitals of the gas atoms and the d orbitals of Cu. Furthermore, Cu-Ti₃C₂O₂ showed the largest difference in adsorption energy between Xe and Kr, demonstrating its strong potential as an effective material for Xe/Kr separation.